Do not use named ETS tables during module definition

Tables named after modules are very likely to be used
the application itself, which can lead to conflicts in
scenarios such as code reloading.

Closes #6361

Author: José Valim

lib/elixir/src/elixir_expand.erl

@@ -451,12 +451,12 @@ expand(Function, E) when is_function(Function) ->
 expand(PidOrRef, E) when is_pid(PidOrRef); is_reference(PidOrRef) ->
   case ?key(E, function) of
     nil ->
-      PidOrRef;
+      {PidOrRef, E};
     Function ->
       %% TODO: Make me an error on 2.0
       elixir_errors:form_warn([], ?key(E, file), ?MODULE,
                               {invalid_pid_or_ref_in_function, PidOrRef, Function}),
-      PidOrRef
+      {PidOrRef, E}
   end;
 
 expand(Other, E) when is_number(Other); is_atom(Other); is_binary(Other) ->

lib/elixir/src/elixir_module.erl

@@ -23,10 +23,10 @@ put_compiler_modules(M) when is_list(M) ->
 %% Table functions
 
 data_table(Module) ->
-  Module.
+  ets:lookup_element(elixir_modules, Module, 2).
 
 defs_table(Module) ->
-  ets:lookup_element(elixir_modules, Module, 2).
+  ets:lookup_element(elixir_modules, Module, 3).
 
 is_open(Module) ->
   ets:lookup(elixir_modules, Module) /= [].
@@ -160,17 +160,17 @@ check_module_availability(Line, File, Module) ->
 
 build(Line, File, Module, Lexical) ->
   case elixir_code_server:call({lookup, Module}) of
-    [{Module, _, OldLine, OldFile}] ->
+    [{Module, _, _, OldLine, OldFile}] ->
       Error = {module_in_definition, Module, OldFile, OldLine},
       elixir_errors:form_error([{line, Line}], File, ?MODULE, Error);
     _ ->
       []
   end,
 
-  Data = ets:new(Module, [set, public, named_table]),
+  Data = ets:new(Module, [set, public]),
   Defs = ets:new(Module, [duplicate_bag, public]),
   Ref  = elixir_code_server:call({defmodule, self(),
-                                 {Module, Defs, Line, File}}),
+                                 {Module, Data, Defs, Line, File}}),
 
   DocsOnDefinition =
       case elixir_compiler:get_opt(docs) of

lib/elixir/test/elixir/module_test.exs

@@ -307,6 +307,12 @@ defmodule ModuleTest do
     end
   end
 
+  test "does not use ETS tables named after the module" do
+    in_module do
+      assert :ets.info(__MODULE__) == :undefined
+    end
+  end
+
   ## Definitions
 
   test "defines?" do